sexual conflict
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2022 ◽  
Vol 25 ◽  
pp. 7-15
Author(s):  
Mingzi Xu ◽  
Ola M. Fincke

In sexual conflict, males are often thought to gain fitness benefits from harassing females over mating. Yet when harassment itself incurs costs to males and if alternative, receptive females are available in a local population, theory predicts that when confronted with a female refusal, a male’s choice of persisting or retreating is determined in part by the likelihood of achieving a mating. We tested that prediction in the damselfly Enallagma hageni, whose males compete by intense scramble competition, resulting in widespread mating harassment toward females, which have a high level of control over mating. Using captive individuals of E. hageni in outdoor insectaries, we quantified male persistence in mating after refusals by pre- and post-oviposition focal females whose egg content we quantified after observations. We documented a novel, context-dependent head-turning refusal signal of sexual non-receptivity, most often displayed in tandem pairs by post-oviposition females that typically carried few mature eggs for males to fertilize. Male persistence was less likely to result in mating with post-oviposition females compared with pre-oviposition females carrying a clutch of mature eggs. Accordingly, males were less likely to persist following refusal signals given by post-oviposition females, supporting the theoretical prediction. Compared with a refusal signal known as wing spread, head-turning was significantly more effective in deterring harassing males. Our results suggest that despite on-going sexual conflict over mating, cooperation benefits both sexes when females use the honest signal of non-receptivity because they carry few mature eggs that males could fertilize.


2021 ◽  
Author(s):  
Michael Hawkes ◽  
Sarah M. Lane ◽  
James Rapkin ◽  
Kim Jensen ◽  
Clarissa M. House ◽  
...  

2021 ◽  
Vol 288 (1965) ◽  
Author(s):  
Thomas J. Hitchcock ◽  
Andy Gardner

Recent years have seen an explosion of theoretical and empirical interest in the role that kin selection plays in shaping patterns of sexual conflict, with a particular focus on male harming traits. However, this work has focused solely on autosomal genes, and as such it remains unclear how demography modulates the evolution of male harm loci occurring in other portions of the genome, such as sex chromosomes and cytoplasmic elements. To investigate this, we extend existing models of sexual conflict for application to these different modes of inheritance. We first analyse the general case, revealing how sex-specific relatedness, reproductive value and the intensity of local competition combine to determine the potential for male harm. We then analyse a series of demographically explicit models, to assess how dispersal, overlapping generations, reproductive skew and the mechanism of population regulation affect sexual conflict across the genome, and drive conflict between nuclear and cytoplasmic genes. We then explore the effects of sex biases in these demographic parameters, showing how they may drive further conflicts between autosomes and sex chromosomes. Finally, we outline how different crossing schemes may be used to identify signatures of these intragenomic conflicts.


2021 ◽  
Author(s):  
Madilyn Marisa Gamble ◽  
Ryan G Calsbeek

Alternative reproductive tactics (ARTs) are ubiquitous throughout the animal kingdom and widely regarded as an outcome of high variance in reproductive success. Proximate mechanisms underlying ARTs include genetically based polymorphisms, environmentally induced polymorphisms, and those mediated by a combination of genetic and environmental factors. However, few ultimate mechanisms have been proposed to explain the maintenance of ARTs over time, the most important of which have been disruptive and negative frequency-dependent selection. Here we explore the role that intralocus sexual conflict may play in the maintenance of sex-specific ARTs. We use a genetically explicit individual-based model in which body size influences both female fecundity and male tactic through a shared genetic architecture. By modeling ART maintenance under varying selection regimes and levels of sex-specific gene expression, we explore the conditions under which intralocus sexual conflict can maintain a hypothetical ART defined by larger (alpha) and smaller (beta) tactics. Our models consistently revealed that sexual conflict can result in the persistence of a sex-specific polymorphism over hundreds of generations, even in the absence of negative frequency-dependent selection. ARTs were maintained through correlated selection when one male ART has lower fitness but produces daughters with higher fitness. These results highlight the importance of understanding selection on both sexes when attempting to explain the maintenance of ARTs. Our results are consistent with a growing literature documenting genetic correlations between male ARTs and female fitness, suggesting that the maintenance of sex-specific ARTs through intralocus sexual conflict may be common and widespread in nature.


2021 ◽  
Vol 9 ◽  
Author(s):  
Katarzyna Wojczulanis-Jakubas

Because there are basic sexual differences in reproductive potential, and the cost of parental care is assumed to be high, biparental care is viewed as a constant tug-of-war between the partners. This raises the question of the system’s evolutionary stability. Several models have been proposed to resolve this problem but none has received unequivocal support. Here, I propose a framework that not only integrates the earlier theoretical ideas (sealed bids, negotiation) but also considers the importance of the environment (frequently neglected in previous models) and views the cost of parental care from a different perspective (costly in terms of parent’s survival only when performed close to the boundary of parental capacity). The framework suggests that sexual conflict may not be such a significant factor mediating parental care as commonly assumed, and that a parent trying to shift the parental burden onto the partner – assumed to be the winner in the tug-of-war interplay – is actually more likely to be a loser, as doing so may put the success of the current breeding attempt in jeopardy, thereby reducing overall fitness of the parent. Once it is realized that the importance of sexual conflict is actually much less than it seems, it becomes clear that the stability of the biparental care system no longer seems to be such a puzzling issue.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maaike Griffioen ◽  
Arne Iserbyt ◽  
Wendt Müller

AbstractSexual conflict arises when two individuals invest in their common offspring because both individuals benefit when their partner invests more. Conditional cooperation is a theoretical concept that could resolve this conflict. Here, parents are thought to motivate each other to contribute to provisioning visits by following the rules of turn taking, which results in equal and efficient investment. However, parents have other tasks besides provisioning, which might hinder taking turns. To investigate restrictions by other care tasks and whether turn taking can be used to match investment, we manipulated brooding duration in female blue tits (Cyanistes caeruleus) during the early nestling phase by changing nest box temperature. As expected, females subjected to cold conditions brooded longer than females under warm conditions. Yet, contrary to our prediction, females had similar visit rates in both treatments, which suggests that females in the cold treatment invested more overall. In addition, the females’ turn taking level was higher in the more demanding cold condition (and the calculated randomised turn taking levels of females did not differ), hence females don’t seem to be restricted in their turn taking strategy by other care tasks. However, males did not seem to match the females’ turn taking levels because they did not adjust their visit rates. Thus, level of turn taking was not restricted by an other sex-specific task in females and did not facilitate a greater investment by their male partners.


2021 ◽  
Author(s):  
Yubing Ma ◽  
Zeyuan Hua ◽  
Aijia Mao ◽  
Daiqin Li ◽  
Shichang Zhang

Abstract Sexual conflict is common in animals, and female sexual cannibalism represents an extreme form of sexual conflict. Males in many species have evolved a variety of strategies to circumvent or decrease the risk of female sexual cannibalism. Opportunistic mating, by which a male mates with a female when she is disturbed or when she is feeding or undertaking moulting, is one of such kinds of strategies, and widely occurs in many animals, especially in spiders. However, whether the occurrence of male opportunistic mating depends on the intensity of female sexual cannibalism remains largely unexplored. We predicted a positive correlation between them. In this study, we tested this prediction by performing a series of mating trials in the laboratory using three species of web-building spiders with different intensities of female sexual cannibalism: Nephila pilipes, Nephilengys malabarensis, and Parasteatoda tepidariorum. We found that the occurrence of male opportunistic mating was positively, though not statistically significantly, correlated with the intensity of female sexual cannibalism, thus supporting our hypothesis. All together, we provide evidence that male opportunistic mating may have evolved to respond to the selection pressure posed by female sexual cannibalism.


Author(s):  
Ana Marquez-Rosado ◽  
Clara García-Có ◽  
Claudia Londoño-Nieto ◽  
Pau Carazo

Sexual selection frequently promotes the evolution of aggressive behaviours that help males compete against their rivals, but which may harm females and hamper their fitness. Kin selection theory predicts that optimal male-male competition levels can be reduced when competitors are more genetically related to each other than to the population average, contributing to resolve this sexual conflict. Work in Drosophila melanogaster has spearheaded empirical tests of this idea, but studies so far have been conducted in lab-adapted populations in homogeneous rearing environments that may hamper kin recognition, and used highly skewed sex ratios that may fail to reflect average natural conditions. Here, we performed a fully factorial design with the aim of exploring how rearing environment (i.e. familiarity) and relatedness affect male-male aggression, male harassment, and overall male harm levels in a natural population of Drosophila melanogaster, under more natural conditions. Namely, we: a) manipulated relatedness and familiarity so that larvae reared apart were raised in different environments, as is common in the wild, and b) studied the effects of relatedness and familiarity under average levels of male-male competition in the field. We show that, contrary to previous findings, groups of unrelated-unfamiliar males were as likely to fight with each other and harass females than related-familiar males, and that overall levels of male harm to females were similar across treatments. Our results suggest that the role of kin selection in modulating sexual conflict is yet unclear in Drosophila melanogaster, and call for further studies that focus on natural populations and realistic socio-sexual and ecological environments.


2021 ◽  
Author(s):  
Manas Geeta Arun ◽  
Tejinder Singh Chechi ◽  
Rakesh Meena ◽  
Shradha Dattaraya Bhosle ◽  
Srishti ◽  
...  

Divergence in the evolutionary interests of males and females leads to sexual conflict. Traditionally, sexual conflict has been classified into two types: inter-locus sexual conflict (IeSC) and intra-locus sexual conflict (IaSC). IeSC is modeled as a conflict over outcomes of intersexual reproductive interactions mediated by loci that are sex-limited in their effects. IaSC is thought to be a product of selection acting in opposite directions in males and females on traits with a common underlying genetic basis. While in their canonical formalisms IaSC and IeSC are mutually exclusive, there is growing support for the idea that the two may interact. Empirical evidence for such interactions, however, is limited. Here, we investigated the interaction between IeSC and IaSC in Drosophila melanogaster. Using hemiclonal analysis, we sampled 39 hemigenomes from a laboratory-adapted population of D. melanogaster. We measured the contribution of each hemigenome to adult male and female fitness at three different intensities of IeSC, obtained by varying the operational sex-ratio. Subsequently, we estimated the intensity of IaSC at each sex-ratio by calculating the intersexual genetic correlation for fitness and the proportion of sexually antagonistic fitness-variation. Our results indicate a statistically non-significant trend suggesting that increasing the strength of IeSC ameliorates IaSC in the population.


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